The cooperating top and bottom die assemblies of the present invention have many applications and can be used whenever it is desired to fold one or more edges of a non-rigid workpiece. While not intended to be so limited, for purposes of an exemplary showing the present invention will be described in its application to the manufacture of parts for the shoe industry.
It is usual practice in the manufacture of shoes to fold some at least of the edges of the individual parts making up the shoe upper so that they present finished edges. The edges of the workpiece to be folded are generally coated with a rubber base adhesive or the like so that they become temporarily bonded after the folding step. Thereafter, the folded edges are additionally stitched together. Alternatively, the edges may be coated with a permanent adhesive and the stitching step eliminated. The various types of adhesive used by the industry are well known and do not constitute a part of the present invention. They may be contact adhesives, heat reactive adhesives or the like.
Heretofore, prior art workers have provided cooperating top and bottom die assemblies for folding the edges of parts such as shoe vamps and the like. Exemplary top and bottom die assemblies are taught, for example, in U.S. Pat. Nos. 3,073,141 and 3,382,687. Such die assemblies performed well but were characterized by certain drawbacks. First of all, they were relatively heavy and complex in construction and, in order to complete a 180.degree. fold in the workpiece edge, it was necessary to cycle the press once, shift a portion of the bottom die assembly, and then recycle the press.
Thereafter, prior art workers developed top and bottom die assemblies of such nature that the workpiece edges could be folded a full 180.degree. with a single cycle of the press. A modified version of this type of top and bottom die assemblies is taught in U.S. Pat. No. 4,051,569. The top and bottom die assemblies of the last mentioned patent differed from the more usual type of such top and bottom dies assemblies in that the top die assembly had a stripper mounted on a floating plate independently operated by additional cylinders mounted on the press, rather than a stripper spring-mounted on the top plate of the top die assembly. This last mentioned patent also taught further modifications for the die assemblies whereby they could be used to seal the folded edges of the workpiece by means of high frequency electricity.
While top and bottom die assemblies of the type just discussed represented significant advances in the art, they two were characterized by certain deficiencies. First of all, the die assemblies were complex in construction and heavy, making handling of the top and bottom die assemblies during die assembly change-over more difficult. The top die, for example, required the presence of not only an intermediate floating plate to support the stripper, but also a top plate. Furthermore, the post and pin arrangement of the bottom die assembly frequently required that clearance holes be provided in one or more plates of the top die assembly to accommodate the pins of the bottom die assembly. This, among other things, limited the useful surface area of the top and bottom die assemblies.
The present invention is directed to improvements in the top and bottom die assemblies of the general type taught in the above mentioned U.S. Pat. No. 4,051,569. The die assemblies of the present invention are easier to manufacture, easier to service and lighter in weight, making them easier to handle during die assembly change-over. The post and pin arrangement of the bottom die assembly eliminates any need for clearance holes in the top die assembly for the pins of the bottom die assembly. This not only gives more working area on both die assemblies, but also eliminates the danger of having a portion of the operator's hands punctured or severed by the pins of the bottom die assembly, if his hands are inadvertently caught between the die assemblies. Furthermore, the post and pin arrangement of the bottom die assembly enables the provision of a deeper pocket (i.e. a thicker cavity plate) in a bottom die of preset overall dimensions. The normal position of the male plug of the bottom die assembly can readily be adjusted to accommodate for the application of a lining or the like to the workpiece, if desired.
The particular arrangement of posts on the top die assembly enables the elimination of a top plate and in many instances the elimination of an intermediate or floating plate as well. This greatly reduces the weight of the top die assembly.
The top and bottom die assemblies of the present invention provide fewer problems of alignment of parts. The die assemblies can readily be modified to apply heat to the folded edges of the workpiece, as will be described hereinafter. The construction of the top die assembly is such that it can readily accommodate a very thin, narrow stripper as will be shown.
In the normal use of such die assemblies, the stripper remains in contact with the workpiece throughout the folding procedure. There are instances, however, when it would be desirable to disengage the stripper from the workpiece during the final portion of the folding procedure. This is true, for instances, when the edges of a very narrow workpiece are being folded and the stripper would be in the way of the final folding step. It has also been found that when the die assemblies are used to apply heat to the workpiece edges, if the stripper remains in contact with the workpiece it will cause undesirable marking of the rear side of the workpiece or of the lining for the workpiece, if a lining is present.
The die assemblies of the present invention may readily be provided with means for causing the stripper to be disengaged from the workpiece during the final portion of the folding procedure and/or during the application of heat to the folded edges of the workpiece or to a lining being applied to the workpiece. These stripper disengagement means constitute parts of the die assemblies, themselves, and no additional cyliners, or the like, are required for the press. Finally, the die assemblies of the present invention can be both of the cavity and plug types, as will be described.